What Is Fermenting?

Step 1 of 5

Microbes eat sugar and leave something behind.

Yeasts and certain bacteria break sugar down without needing air, and what they leave is acid, alcohol or gas. That leftover is the whole point.

Step 2 of 5

What they leave keeps everything else out.

Acid and alcohol are hostile to most of the things that would spoil food. A fermented food defends itself, which is why it keeps for months without a fridge.

Step 3 of 5

The trick is stacking the odds first.

Salt, a lack of air, or a starter culture handicaps everything except the microbe you want. Then it wins on its own — you never have to keep anything else out by hand.

Step 4 of 5

It appears in every cuisine on earth.

Bread, cheese, yoghurt, pickles, soy sauce, vinegar, tea and chocolate are all fermented. It was the main way of keeping food long before refrigeration existed.

Step 5 of 5

Flavour is the side effect worth having.

Microbes break big bland molecules into small sharp ones. That is why fermented food tastes stronger than what it was made from, and why nothing else tastes quite like it.

Fermenting was understood and used for thousands of years before anyone knew microbes existed at all.